https://astralcodexten.substack.com/p/impact-market-mini-grants-update
Impact markets are a charity analogy to private equity. Instead of prospectively giving grants to projects they hope will work, charitable foundations retrospectively give grants to projects that did work. Investors fund those projects prospectively, then recover their money through the grants. This offloads the responsibility of predicting which projects will succeed - and the risks from unsuccessful projects - from charitable foundations to investors with skin in the game.